Ringed tubes, that is to say tubes whose form resembles a succession of rings connected to one another, are usually produced from plastic, such as extruded polypropylene. Such tubes enable complex protective sheath systems to be produced for electric wire or cable harnesses within a vehicle, such as a car or lorry, and particularly in the engine compartment. In fact, because of the small amount of space available, these sheaths or hoses have to be able to follow the non-rectilinear walls very closely and pass around the different components encountered. With such ringed sheaths it is just possible to produce curves with a radius of curvature less than three times their diameter without their deforming on the inside or even breaking.
Current developments in motor car technology, particularly in the domain of electrical accessories such as high-fidelity loudspeakers, rear screen wipers, etc, and in the continuous electronic monitoring of many parameters resulting in automatic commands, means that more and more electric cables pass through different bodywork components, such as doors or roof fittings, to reach the fascia for example. Moreover, particular efforts are currently made to improve the soundproofing of the passenger compartment, by systematically seeking out and eliminating all potential sources of noise. It has been found, however, that the vibration of cables harnesses inside sheaths, or of sheaths against wall members, may generate auditory nuisances.